Quiz 4 Flashcards
In a laboratory experiment you have treated a muscle cell with a calcium channel blocker. The membrane can still depolarize, but the concentration of calcium cannot increase in the sarcoplasm. Which of the following describes what will happen next?
Tropomyosin will continue to cover the myosin binding sites on actin and no cross bridges will form.
Slow twitch oxidative muscle fibers would be the predominant fiber recruited during a marathon run because ________
the fiber would provide sustained amounts of ATP for muscle contraction
The factor(s) that determine the duration of a twitch in various types of fibers is the speed of the
removal of Ca2+ ions from the sarcoplasm only.
Which is a FALSE statement about skeletal muscle structure?
A myofibril is composed of multiple muscle fibers.
Which of the following statements regarding skeletal muscle is TRUE?
A given skeletal muscle fiber will contract if its associated motor neuron fires an action potential.
An important difference between single-unit and multiunit smooth muscle is the
numerous gap junctions in single-unit smooth muscle, which allow many cells to work together as a sheet.
Subunits of skeletal muscle fibers that are composed of sarcomeres are called ____________.
myofibrils
Choose the description of an event that does NOT happen during the cross-bridge cycle.
Energized myosin heads bind troponin.
Put these events in the correct chronological sequence:
- End-plate potentials trigger action potentials.
- Transverse tubules bring potentials into the interior of the cell.
- Acetylcholine binds to receptors on the motor end plate.
- Ca2+ is released from the sarcoplasmic reticulum.
3, 1, 2, 4
Each somatic motor neuron with all the muscle fibers it innervates is a __________.
motor unit
The muscles in your fingers have a predominance of fast-glycolytic fibers, whereas the muscles of your feet have a predominance of slow-oxidative fibers. Which of the following statements accurately describes the differences between the two types of skeletal muscles?
Muscle fibers of the feet have a greater abundance of myoglobin than do muscle fibers of the hands.
In smooth muscle cells, ________ functions in a manner analogous to troponin.
calmodulin
In the first few seconds of skeletal muscle contraction, what is the main mechanism of ATP replenishment?
Phosphate group is transferred from creatine phosphate to ADP.
Which CORRECTLY characterizes a “fast-oxidative-glycolytic” type of skeletal muscle fiber?
high myoglobin content and intermediate glycolytic activity
The calcium required for the skeletal muscle contraction _____________.
is passively released from the sarcoplasmic reticulum
What structures carry the action potentials into the interior of the muscle to cause muscle contraction?
T tubules
The function of myosin light chain kinase in smooth muscle is to
phosphorylate myosin light chains, enhance myosin ATPase activity, thus driving actin binding.
A change in smooth muscle cell contraction in the absence of a change in electrical potential of the cells is described as a(n)
pharmacomechanical coupling.
The relaxation of skeletal muscle relies on the activity of the ________, which decreases cytoplasmic calcium concentration.
Ca2+-ATPase
The name given to the repeating functional units that cause striations in a skeletal muscle myofibril is “sarcomere.”
True
Compared to type 1, both forms of type 2 muscle fibers usually have a larger diameter.
True
